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Colorado River Boundary Section

The two Governments through the IBWC jointly administer the terms of Related Links Water Bulletins the 1944 Water Treaty relating to the Colorado River, which provides that of its waters there are allotted to Mexico, (a) a guaranteed annual quantity of 1,500,000 acre-feet (1,850,234,000 cubic meters) and (b) any other quantities arriving at the Mexican points of diversion with certain conditions stipulated in the 1944 Treaty. The application of these terms began in 1950. The operations are performed in collaboration with the United States Bureau of Reclamation, Department of the Interior.

Treaty Deliveries to Mexico

The procedure is as follows: Mexico, before the first of each calendar year, presents through the IBWC and annual schedule of requested deliveries by months, within the Treaty annual allotment and specified rates.  Mexico also submits a weekly schedule

of deliveries by day, within the monthly amounts scheduled. Mexico's requests are transmitted by the United States Section to the Bureau of Reclamation, which makes the releases as necessary from the United States storage works on the Colorado River to fulfill the delivery schedule. The deliveries to Mexico are jointly monitored by the IBWC to ensure compliance with the Treaty allotment and schedules. For this purpose, the 1944 Treaty also provides that the IBWC shall construct, operate and maintain the boundary section of the Colorado River, and in each country its Section of the IBWC construct, operate and maintain all necessary gaging stations and other measuring devices for the purpose of keeping a complete record of the waters delivered to Mexico and of the flows of the Colorado River downstream of Imperial Dam in the United States. Pursuant thereto, the IBWC jointly operates and maintains six gaging stations on the Colorado River. The United States Section operates and maintains five other gaging stations for Treaty purposes. The field data collected are jointly compiled and reviewed by the IBWC. Records of the flows of the Colorado River reaching Mexican points of diversion are published annually in IBWC bulletins entitled, "Colorado River and other Western Boundary Streams," in English and Spanish. Copies of the bulletins in English may be obtained from the United States Section office in El Paso, Texas. Morelos Diversion Dam Project Pursuant to the 1944 Water Treaty, Mexico constructed at its expense and under the supervision of the IBWC a main diversion structure in the limitrophe section of the Colorado River, to enable that country to divert the major part of its allotted waters from the river. The waters diverted are used to irrigate the extensive and highly-developed lands in the Mexicali Valley. The dam is located 1.1 miles (2 km) downstream from the point where the California-Baja California land boundary intersects the river. The dam was completed in 1950. This structure, named Morelos Dam after one of Mexico's foremost patriots, is of reinforced concrete spanning 1,400 feet (426.72 m) across the Colorado River. It supports 20 electrically-operated, radial gates to control stages of the Colorado River to enable diversions through the adjoining intake structure that supports 12 radial gates which control diversions westward to the canal system in Mexico. The river part of the dam is designed to pass a flood of 350,000 cfs (9,911 cms) and the intake structure is designed to pass 8,000 cfs (226 cms). Morelos Dam is operated and maintained by Mexico under the supervision of the IBWC.

Protective Levees Upstream of Morelos Dam

Pursuant to the terms of the 1944 Water Treaty, the river levees along the Colorado River in the United States upstream from Morelos Diversion Dam and along the Gila River near Yuma, Arizona were raised, as jointly determined by the IBWC, to protect hands in the United States against such flood damage as might result from the construction and operation of the diversion dam. The major parts of the levees were raised by the United States in 1951 and 1952 and the remaining part in 1964. Mexico paid the costs of raising of the 41.9 miles (67 km) of levees. The work was performed by the United States Bureau of Reclamation under the supervision of the IBWC. Mexico also pays the costs for maintenance of that part of the levees raised because of Morelos Dam.

Colorado River Flood Control Project

Under the 1944 Water Treaty the IBWC recommended and the two Governments approved a joint project to maintain clear of vegetation the channel of the Colorado river and adjoining floodplain through the approximately 20 mile (32.2 km) boundary section of the river from Morelos Diversion Dam downstream to the point where the Arizona-Sonora boundary intersects the river, and further downstream therefrom a distance of about 20 miles (32.2 km) in Mexico.

United States participation was authorized by the Act of Congress of August 10, 1964, as amended. The initial clearing was jointly performed in 1964 and maintenance clearing is similarly performed annually, under the joint supervision of the IBWC.

This project serves to maintain the flood-carrying capacity of the channel and floodway formed by levees on the United States bank and on the Mexican bank in the boundary section of the river, and downstream therefrom on both banks in Mexico, thereby guarding against flooding of extensive irrigated agricultural lands in the United States and in Mexico. The effectiveness of the clearing was demonstrated during high discharges in 1980, when the project enabled the flows to naturally scour and improve the river channel.

Project for Permanent and Definitive Solution to the International Problem of the Salinity of the Colorado River

In 1965, the two Governments approved recommendations of the IBWC for a five-year-agreement for remedial measures and procedures by the United States to alleviate the problem which arose in 1961-1962 of increased salinity of the Colorado River treaty deliveries to Mexico, caused by saline drainage waters originating in the United States. The agreement was extended for two years to 1972. It provided for the construction and operation by the United States of a bypass channel, which could pass to the river downstream of Morelos Dam a part of the saline drainage waters and enable substitution therefor of low salinity waters. Pursuant to a further interim agreement of the IBWC in 1972, the salinity of the waters delivered to Mexico was further reduced by passing to the river downstream of Morelos Dam an additional part of the saline drainage waters and substituting therefor additional waters of low salinity.

On August 30, 1973, agreement was reached by the two Governments under the terms of the 1944 Water Treaty for a "Permanent and Definitive Solution to the International Problem of the Salinity of the Colorado River." The agreement was negotiated by ambassador Herbert Brownell, Jr., Special Representative for the United States, and the Secretary of Foreign Relations of Mexico, Emilio O. Rabasa, and was incorporated in a Minute of the IBWC. This agreement provided for immediate further reduction in the salinity of the waters delivered to Mexico, stipulating that the United States shall adopt measures to assure that the approximately 1,360,000 acre-feet (1,677,545,000 cubic meter) delivered upstream of Morelos Dam, have an annual average salinity of no more that 115+30 parts per million (ppm) over the annual average salinity of the Colorado River at Imperial Dam. The United states Congress in the Colorado River Salinity Control Act of June 24, 1974, as amended, authorized the United States Bureau of Reclamation, Department of the Interior, to construct the works required to implement the agreement in the United States. The terms of the agreement were immediately put into effect by interim measures consisting of the bypassing to the Gulf of California of all of the saline drainage waters which created the problem and substituting therefor water of low salinity.

For this purpose the authorization included extension in the United States and in Mexico of the bypass drain to carry the drainage and later the reject waters from a desalting plant to the Santa Clara Slough in Mexico on the Gulf of California. The extension of the bypass drain was completed in June 1977 with the part in Mexico constructed by its Government at the expense of the United States through arrangements made by the IBWC.

Compliance with the agreement is jointly monitored by the United States and Mexican Sections of the IBWC. The waters delivered upstream from Morelos Dam are jointly sampled each weekday and they are analyzed for their salt content by the United States Section and the Mexican Section, and the results are jointly compared by the IBWC. The records show that the United States is fully complying with the terms of the agreement.

The Congress of the United States recognized that to continue the interim measures to implement the agreement with Mexico would result in a serious loss of water needed to meet uses within the Colorado River Basin in the United States. To prevent such loss, the Congress in the Salinity Control Act authorized the Secretary of the Interior to construct, operate and maintain a desalting plant and appurtenant works in the United States to reduce the salinity of drain waters from the Wellton-Mohawk Irrigation and Drainage District, to enable their delivery to Mexico within the terms of the agreement. The Department of the Interior has started construction of the desalting plant located just west of Yuma, Arizona. The desalting complex is scheduled for completion in 1987.

Boundary Mapping-Colorado River

As in the case of the Rio Grande, the 1970 Boundary Treaty provides that the IBWC shall carry out as soon as practical the necessary surveys and shall, with appropriate precision, delineate the international boundary on maps or aerial photographic mosaics of the Colorado River. The United States Section was authorized to participate in this joint undertaking by the American-Mexican Boundary Treaty Act of October 25, 1972.

The boundary follows the middle of the Colorado River for a river distance of 24 river miles (38 km) from the point where the California-Baja California land boundary intersects the river to the point where the Arizona-Sonora land boundary intersects the river.

Aerial photographic maps of this section of the boundary were completed in 1975 and the location of the boundary in the middle of the river was jointly delineated thereon by engineers of the two Sections of the IBWC. The maps were adopted by the IBWC on September 23, 1986. The total costs of the surveys are divided equally as prescribed by the 1970 Treaty.

Copies of the maps may be reviewed in the Headquarters of the United States Section and the Mexican Section in El Paso, Texas and Ciudad Juárez, Chihuahua, respectively. In the United States, copies of the maps may be obtained through the United States Geological Survey in Denver, Colorado.